Following the Kojiki is the Nihon Shoki (720 AD), which records the first sumo bout between two real men and in the process determine who the the "father of sumo" is. Nomi no Sukune of Izumo was supposedly asked by the Emperor Suinin to fight Taima no Kehaya of Nara. Since sumo in these days was a no-holds barred affair, Sukune was able to mortally kick Kehaya above the belt and win the match. Sukune thus became known as the first rikishi.
It is acknowledged by historians, however, that sumo is about 1,500 years old. Like most Japanese traditional arts, sumo is closely associated with Shinto, and the rituals that rikishi perform today, along with the decorations they put in their heya (stable) as well as the ones they wear, are part of Shinto ritual usually associated with agriculture.
Near the end of the Edo period, when there was great debate regarding the opening of the ports to Western demand, sumo was also undergoing a great change from old great fighters such as Yokozuna Tanikaze and Ozeki Raiden, to a new generation of fighters. This was also the time when politics came to play a role in the granting of Yokozuna titles: pure merit was not the sole consideration, but also the daimyo (feudal lord) to whom a rikishi belonged.
When Commodore Perry arrived, it was the rikishi who carried the gifts of the shogunate to the American warships. It was also this group of Americans who were probably the first Westerners to see sumo, when they were invited for an exhibition bout. Perry, probably baffled and disgusted, wrote in his journal, "[W]hether the [bout] was to imitate the actions of a bull...or for what purpose, I am ignorant, but it seemed to be very foolish" (Roger Pineau, ed. The Japan Expedition, 1852-1854: The Personal Journals of Commdore Matthew C. Perry, Washington, D.C.: Smithsonian University Press, 1968; quoted in Hall, p. 14).
Little did Perry know that more than a hundred years later, an American with the shikona (fighting name) "Akebono" ("sunrise") would reach the pinnacle of sumo as yokozuna.
By the turn of the century, sumo became the country's national sport and was patronized by politicians and industries. It must also be noted that "further interest was aroused in sumo as a symbol of strength when Japan emerged victorious in the Sino-Japan War" (Sharnoff, p. 44). In 1909 a kokugikan (national sport arena) was built. By 1928 sumo became even more modern with live radio broadcasts and the setting of time limits for shikiri (pre-bout toeing the mark). The 1930s saw the emergence of the great Futabayama, who took sumo to new heights of popularity. Sumo became a required subject for boys' physcial education classes in grade school.
As Japanese society under the Allied forces underwent major reforms, so did the sumo world. Further professionalization was carried out within the kyokai, which also established a school for new recruits. Most of the rules of toshiyori kabu (elders' stock) and heya mochi (stable ownership) were created during this period. Recruitment qualifications were done according to the Monbusho (Ministry of Education) policy of gimu kyoiku (compulsary education), so recruits could only formally enter after graduation from junior high school. The system of six tournaments a year was also established. Rules for gakusei-zumo (boys with varsity sumo experience) were set. By the 1960s sumo became the professional sport we know today.
Tradition dictates the contents of a rikishi's daily regimen. Training is supposed to involve only the traditional keiko activities such as butskari-geiko, shiko (foot stomping), teppo (pole hitting), suriashi (shuffling), matawari (splits) and sonkyo (meditative breathing). However, the emergence of the great Yokozuna Chiyonofuji changed the accepted training regimen for good. Chiyonofuji, who was neither very big nor tall, developed a strict regimen of modern weight training and body building using Western gym technology. Initially, this was frowned upon by the traditionalists who ruled the Kyokai, but then Chiyonofuji became the most powerful rikishi in the 1980s and took sumo to new heights of national and international popularity. Today, the use of Western-style machines is common for many sumo-beya, and a few actually have a fully equipped gym. Now, rikishi are actually encouraged to take up other sports to help their overall athleticism, although of course the traditional keiko is still strictly enforced as the main form of training.
Note: The historic artifacts illustration above was scanned from the Sumo Museum's brochure. This tiny but highly interesting museum can be found in the Kokugikan (National Sport Arena) at Ryogoku, north of downtown Tokyo.